Convert examples/node/pdf2svg.js to await/async #14125

Author: stbensonimoh

examples/node/pdf2svg.js

@@ -70,73 +70,70 @@ ReadableSVGStream.prototype._read = function () {
 };
 
 // Streams the SVG element to the given file path.
-function writeSvgToFile(svgElement, filePath) {
+async function writeSvgToFile(svgElement, filePath) {
   let readableSvgStream = new ReadableSVGStream({
     svgElement,
   });
   const writableStream = fs.createWriteStream(filePath);
-  return new Promise(function (resolve, reject) {
-    readableSvgStream.once("error", reject);
-    writableStream.once("error", reject);
-    writableStream.once("finish", resolve);
-    readableSvgStream.pipe(writableStream);
-  }).catch(function (err) {
+  try {
+    await readableSvgStream.once("error");
+    await writableStream.once("error");
+    await writableStream.once("finish");
+    await readableSvgStream.pipe(writableStream);
+  } catch (err) {
     readableSvgStream = null; // Explicitly null because of v8 bug 6512.
     writableStream.end();
     throw err;
-  });
+  }
 }
 
-// Will be using promises to load document, pages and misc data instead of
+// Will be using async/await to load document, pages and misc data instead of
 // callback.
-const loadingTask = pdfjsLib.getDocument({
-  data,
-  cMapUrl: CMAP_URL,
-  cMapPacked: CMAP_PACKED,
-  fontExtraProperties: true,
-});
-loadingTask.promise
-  .then(function (doc) {
-    const numPages = doc.numPages;
-    console.log("# Document Loaded");
-    console.log("Number of Pages: " + numPages);
+const loadingTask = async function () {
+  const loadTask = pdfjsLib.getDocument({
+    data,
+    cMapUrl: CMAP_URL,
+    cMapPacked: CMAP_PACKED,
+    fontExtraProperties: true,
+  });
+  const doc = await loadTask.promise;
+  const numPages = await doc.numPages;
+  console.log("# Document Loaded");
+  console.log("Number of Pages: " + numPages);
+  console.log();
+
+  let finalResult;
+  const loadPage = async function (pageNum) {
+    const page = await doc.getPage(pageNum);
+    console.log("# Page " + pageNum);
+    const viewport = page.getViewport({ scale: 1.0 });
+    console.log("Size: " + viewport.width + "x" + viewport.height);
     console.log();
 
-    let lastPromise = Promise.resolve(); // will be used to chain promises
-    const loadPage = function (pageNum) {
-      return doc.getPage(pageNum).then(function (page) {
-        console.log("# Page " + pageNum);
-        const viewport = page.getViewport({ scale: 1.0 });
-        console.log("Size: " + viewport.width + "x" + viewport.height);
-        console.log();
-
-        return page.getOperatorList().then(function (opList) {
-          const svgGfx = new pdfjsLib.SVGGraphics(page.commonObjs, page.objs);
-          svgGfx.embedFonts = true;
-          return svgGfx.getSVG(opList, viewport).then(function (svg) {
-            return writeSvgToFile(svg, getFilePathForPage(pageNum)).then(
-              function () {
-                console.log("Page: " + pageNum);
-              },
-              function (err) {
-                console.log("Error: " + err);
-              }
-            );
-          });
-        });
-      });
-    };
+    const opList = await page.getOperatorList();
+    const svgGfx = new pdfjsLib.SVGGraphics(page.commonObjs, page.objs);
+    svgGfx.embedFonts = true;
+    const svg = await svgGfx.getSVG(opList, viewport);
+    let result;
 
-    for (let i = 1; i <= numPages; i++) {
-      lastPromise = lastPromise.then(loadPage.bind(null, i));
+    try {
+      result = await writeSvgToFile(svg, getFilePathForPage(pageNum));
+      console.log("Page: " + pageNum);
+    } catch (err) {
+      console.log("Error: " + err);
     }
-    return lastPromise;
-  })
-  .then(
-    function () {
-      console.log("# End of Document");
-    },
-    function (err) {
-      console.error("Error: " + err);
+    return result;
+  };
+
+  try {
+    for (let i = 1; i <= numPages; i++) {
+      finalResult = loadPage.bind(null, i);
     }
-  );
+    console.log("# End of Document");
+  } catch (err) {
+    console.error("Error: " + err);
+  }
+  return finalResult;
+};
+
+loadingTask();